Markdown is a plain text formatting syntax designed and developed by John Gruber in 2004, so that it can optionally be converted to HTML using a tool by the same name. Markdown is popularly used as format for readme files, or for writing messages in online discussion forums, or in text editors for the quick creation of rich text documents.There are some markdown editors given below:

Markable

Markdown syntax hightlighting, auto indent and unindent, highlight current line, line number, a light and a dark theme. Auto save your content. Resume to latest status when you sign in again, even on another device. You can alsoPreview html format output side by side, in real time. Convert html to markdown when uploading files or import files from other services. Mark the file as public to make it visible to all visitors. You can even use Markable as a mini blog platform. Download markdown source or html output with single click. Fully integrated with Evernote. Import notes into Markable editor. Export your markdown source or html output to Evernote.Markable.in integrates with online storage service Dropbox. Seamlessly saving your markdown file to dropbox. Seamless integration with Tumblr, send html output to Tumblr as blog post.

Minimalist Online Markdown Editor

This is the simplest and slickest online Markdown editor. Just write Markdown and see what it looks like as you type. And convert it to HTML in one click.

Buttons you might want to use:

Quick Reference: that's a reminder of the most basic rules of Markdown

HTML | Preview: HTML to see the markup generated from your Markdown text, Preview to see how it looks like

Privacy:

No data is sent to any server – everything you type stays in your browser

The editor automatically saves what you write locally in case you accidentally close it.

If using a public computer, either empty the left panel before leaving the editor or use your browser's privacy mode

EpicEditor

EpicEditor is an embeddable JavaScript Markdown editor with split fullscreen editing, live previewing, automatic draft saving, offline support, and more. For developers, it offers a robust API, can be easily themed, and allows you to swap out the bundled Markdown parser with anything you throw at it. EpicEditor is set up to allow you to use any parser that accepts and returns a string. This means you can use any flavor of Markdown, process Textile, or even create a simple HTML editor/previewer. Theming is easy in EpicEditor as well.

Mou (Mac)

Available only for Mac users, Mou is a Markdown editor that focuses entirely on developers. It offers features such as syntax highlighting, sync scroll, custom themes, PDF export and enhanced CJK support. Mou also has a separate iPad version.

StackEdit

StackEdit is a free, open-source Markdown editor used by Stack Overflow and the other Stack Exchange sites. StackEdit can:

Manage multiple Markdown documents online or offline

Export your documents in Markdown or HTML and format it using a template

Dillinger has a clean user interface that will help you compose Markdown text easier. This online Markdown editor links up with four web services: Dropbox, Google Drive, One Drive, and even GitHub. You can export your text to HTML, styled HTML, Markdown (.md), and PDF. It has a "distraction-free" mode which hides everything except your Markdown text so you can focus on writing.

Online Markdown Editor

The appjangle edit application is an easy-to-use, free online Markdown editor. It is built as a very fast way to create, publish and share web content. Markdown is a markup languge, whose goal is to enrich plain text files with sensible formatting. For instance, surrounding any word with **bold** will format the text as bold. Markdown in general produces very clear and standard-complaint HTML pages, by allowing to enrich text with standard elements such as h1, em, a etc. There are plenty of resources, which explain all of the various ways in which documents can be formatted with Markdown. It's really worth 5 min to learn this simple, yet powerful language.

How does it work?

The appjangle platform is a powerful web application and content platform. It's main theme is to empower to extend the web. As one part of this, the appjangle platform is built to enable the rapid creation of single web pages or interconnected clusters of web pages.

This Markdown editor builds on the appjangle platform to enable you to:

create new public, persisted web pages in Markdown without need to register

share these pages for public viewing and private editing

optionally register to keep track of a portfolio of pages you create

LightPaper (Mac)

LightPaper is a simple editor for Mac users that offers a distraction-free writing interface. It offers several in-built fonts, and you can also export your content in HTML, PDF or audio files.

WriteMonkey

Writemonkey is a Windows zenware writing application with an extremely stripped down user interface, leaving you alone with your thoughts and your words. It is light, fast and free. With an array of innovative tools under the hood and full Markdown* support, it helps you write better.

Dingus

Dingus is a relatively old and extremely simple Markdown online editor. What makes this tool special is it’s by Daring Fireball (John Gruber), the creator of Markdown. Don’t quote me on this because I’m not sure, but this might very well be the first online Markdown editor.

wri.pe

wri.pe is a simple and smart web notepad. Are you tired of complexity? All you want is just taking notes? Then wri.pe is for you, we focus on simplicity. Dates writen in the title or body of your notes are automatically inserted in your calendar. You can use almost all functions using your keyboard. wri.pe also supports markdown. Access your notes from any location. wri.pe can be used from iPhone/iPad, Android and PC browsers. Your notes are safe at wri.pe with a daily backup to Dropbox and Evernote.

Conclusion

There are a lot of free online Markdown editors out there. However, two of them truly stood out to me: StackEdit and Dillinger. Both of these online Markdown editors have the features needed for practical writing, and that’s why they get my vote.